mellinger



E. A. MELLINGER. TELEPHONE 'EXCHANGE AUTOMATIC, WITVCHING SYSTEM.APPtICATIONHLED SEPT-4, 190a. RENEWED us. 16. m9.

' Patented June 15;1920

3 SHEEJS-SHkET I.

mine hm m mm mm m N E. A.MELLINGER. TELERHONE EXCHANGE AUTOMATICSWITCHINGSYSTEM.

Patented'Jun 15, 1920.

3 SHEETS-SHEET 2.

APPLICATION FILED SEPT-'4. 1908 RENEWED AUG.

E- A. MELLINGER.

TELEPHONE EXCHANGEAUTOMATIC SWITCHING SYSTEM. APPLICATION FILED SEPT-4,190s. ncmzwsu we. 16.1919.

"1,343,462. PatentedJune 15,1920.

3 SHEETSSHLET 3- efli'ciencv of a telephone system uurrso STATES PATENTOFFICE.

TIIHVAIIEtD A. MELLINGER, OF CHICAGO, ILLINOIS. ASSIGNOR T AUTOMATICELECTRIC COMPANY. OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS. t

TELEPHONE-EXCHANGE AUTOMATIC SWITCHING SYSTEM.

Specification of Letters Patent.

Patented June 15. 1920.

Application filed September 4. 1908, Serial No. 451.674. Renewed August16, 1919. Serial No. 318,040.

no operating grounds at the substations, which are cinnmonly calledtwo-wire sysams.

Objects of my invention are the provision of an improved non-numericaltrunking lVltliL-llldt is to say. a switch for automuticully selectingidle trunks without reference to any digit of the called number; theprovision of an improved master switch for controlling the operation ofa plurality of said non-numerical trunking switches,-

n'hercby the latter select idle trunks ahead of the calls: the provisionof an improved selector or numerical trunking switch for a twowiresystem; the provision. of an im-- proved connector switch for findingthe called line: and-the provision of certain details and features ofimprovement and combinations tending to increase the general w 7 of thispar ticlilar character. 1

To the foregoing and other useful ends my invention consists in mattershereinafter set forth and claimed.

In the accompanying drawings Figure 1 shows diagrammatically the callingsubscrihers substation A and the central office switching apparatus of asystem involving the principles offmy invention. To the line ofsubstation A is allotted the line switch (1 controlled by: the masterswitcl1 D. At E is represented a first-selector switch; and at F adiagramof a second-selector switch 1S shown. I

In Fig. 2 there is shown digrammatically a connector switch H, at I acentral ofiioe ringer generator is shown and at 'J'a busysignalingdevice. K represents a device for interrupting the ener iz ing circuitof the ringer re1ay-t hat is, y means of the apparatus K the ringerrelay may be caused to energize intermittently. To the line of stems,and especially to systems that have the substation A there is allottedthe line switch (1" which is like theline switch (7.

Figs. 1 and 2 taken together represent diagrammatically the centralollicc switchinn apparatus involved in establishing a onnection betweentwo substations. In Fig. i a central battery is shown at ll having itspositive terminal preferably grounded at G. The central oflicc switchingapparatus is of thegcneral type disclosed in Eng lish Patent No. 526.301of 1906. but with modifications and circuit changes to adapt the same tooperate in connection with a twowire syste.m-that is. a system in whichthere is no ground connection at the subscribcrs telephone. The lineswitches of which C and C are modified forms are also disclosed. in Thellcsfmn Electrician of January 25, 1908, and the American TelephoneJournal of June 6,1908. The master switch D is also of the formdisclosed in the said llesteru Electrician and the A mcricoin Talc phoneJournal. The first-selector E and second-selector F are of the generalty )e shown in United States Letters Patent i 0. 815,321, granted March13, 1906. to Keith, Erickson and Erickson. while the connector switch His of the general type shown in United States Letters Patent No.815,176, granted March 13, 1906, to Keith, Erickson and Erickson.-

Fi 3 is a diagrammatic View showing t 1e line switch, theline switchplunger and the line switch bank, together with the circuitsand parts ofthe master switch.

The snbscribers substation. it will be. seen, is somewhat dilferent fromthe usual automatic substation, substation A being arranged and modifiedto operate in connection with a two-wire system-that is, a system inwhich no ground connection is used at the subscribers substation.Substation A, for example,'comprises the usual receiver 2, switch-hook3, induction coil, 4 which consists of the primary winding 5 andsecondary winding 6, transmitter 7, condenser '8, ringer 9 and impulsewheel 10, which latter has the usual impulseteeth 11. The impulse wheel10"is secured to the shaft 12, to' iwhi'ch shaft there is also'securedthe dial (not-shown). When the dial is turned the impulse'teeth, 11 areadapted to engage the cam 13 upon the end of the spring 14 and therebycarry the latter out of engagement with the s ring 15. Upon theswitch-hook 6 there is t e cam 16 which, when the switchhook is upermits the springs 17 and 18 to engage, t ereby bridging across thesubscribers line conductors 19 and 20 the rimary .circuit including thetransmitter in series with the primary winding 5; but when theswitch-hook is lowered the spring 21 is carried into engagement with thespring 22, whereby the ringer 9 in series with the condenser 8 isbridged across the line conductors 19 and 20 instead.

The connector switch H (Fig. 2) like the line switch (3 andfirst-selector 1 1, is arranged to operate in a system in which there isno ground connection at the subscribers station.

A clearer understanding of my improved system may be had from anexplanation of its operation when a subscriber operates the centraloiiice switches to establish-a connection. For example, it will bepointed out how the subscriber at substation A may operate the mainoffice switches to establish connection with substation A (Fig. 2), thenumber of which is 2220. To call the number 2220 the subscriber atsubstation A, after removing the receiver from the switch-hook, operatesthe calling device for each digit in the well-known manner. When thereceiver is removed from the switch-hook, and the springs 17 and 18engage, an energizing circuit is closed through the line relay 23 of theline switch C. When this role energizes, a circuit is closed through t etrip or plunger ma net 24, which then operates toforce the p unger intoa bank terminal andextend the calling liiie conductors to a trunk-lineleading to a selector s itch. The dial is operated for the first digit,and upon returning to normal position operates the first-selector switchto establish connection with a trunk-line leading to a second-selectorswitch. The second-selector is thenoperated for the second digit toselect a trunk-line leading to a connector switch. The impulsesdelivered by the dial for the last two digits are directed toward theconnector, which operates to place its shaft wipers in connection withthe contacts corresponding to the desired number. When the substationprimary circuit is bridged across the line conductors 19 and 20 anenergizing circuit is established through the line relav 23, saidcircuit extending from ground G 'hrough the springs 26 and 27 to theline conductor 20, through the transmitter 7 and primary winding 5,impulse springs 14 and 15, springs 17 and 18 to .the line conductor 19,springs 28 and '29, winding of the line relay 23 to the battery lead 25,thence through battery B to ground G. The line relay. upon energizing,ressesthe springs 3H and 31 into contact. 5 shown. the line relay '23 isslow-acting- -that is. when once energized terminal similar gages fromthe spring and the energizing circuit is then broken the relay does notinstantly return to normal position, but remains in its energizedposition for a short interval. The engagement of the springs 30 and 31closes an energizing circuit through the trip or plunger magnet 24,\VlllCll magnet operates to attract the plunger arm and thrust theplunger into an idle bank terminal. The inn er magnet circuit extendsfrom groun G t irough the springs 30 and 31, plunger magnet 24 to thebattery lead 25, thence through battery B to groundG. When the plungerenters the bank terminal and closes the bank springs 32 and 33 intocontact an energizing circuit is closed through the motor magnet relay34, which in turn operates to close a circuit through the motor magnet35 of the master switch D. The motor magnet then operates to advance-allidle plun ers that are in locked engagement witht 1e plunger shaft 36 toa position opposite the next idle bank to the one just engaged. Thecircuit through the motor magnet relay extends fromground G throu h therelay 34to the common segment 0 the master switch bank, wiper 37,individual segment 38, through the bank springs 32 and 33 to thebattery lead 25, etc. .The relay 34, upon energizing, operates to placethe sprin s 39 and 40 in contact, whereby a circuit is c osed throu hthe motor magnet 35, said circuit exten ing from ground G through themotor magnet 35, interrupter springs 41 and 42, motor ma net relaysprings 39 and 40 to the battery ead 25, etc. The motor magnet, uponenergizing, attracts its armature 43, and the pawl 44 engages a tooth ofthe ratchet wheel 45 andmoves the latter one step. iVhen this occursthespring 46 engages the spring 47 (hearing in mind that the spring 46,rior to this 0 oration, engaged a notch o the toothed w ieel 48), and

. when theratchet wheel 45' is given one step the sprin 46 slides offrom the toprofthe notch an engages the spring 47. be engagement ofthese two springs provides a energizing circuit for the motor magnet 35,said circuit extending, through the springs 46 and 47 to the batterylead 25 instead of through the springs 39 rind 40. Furthermore, themotor magnet. when encrnew ' gized, separates the interrupter springs 41and-L2. thereby breaking its own circuit like a buzzer. The motor magnet35 continues to operate in this manner as long as the siring's 46 and 47remain in engagement. llhen the next succeeding tooth on the wheel 48advances far enough the spring 47 disen- 46. thereby opening theenergizing circuit for the motor magnet. By the time the last notchdisengugcsthc springs 46 and 41' the master switch wiper 37 has passedfrom the first contact 38 to the second ontact 49. suppose. however,that when the wiper 37 engages the individual cuit, retains the plungerarm in an attracted segment 49 there then is a guarding potenpositionand the plunger in the bank termitial present. In that event anenergizing nal. Thus it will be seen that the line switch, circuit isclosed through the motor magnet after being operated from thesubscribers 5 relay 34, said circuit extending from the constation, ismaintained in its operated posi- 7o tart through the wiper 37, commonsegment tion by a ground connection at the firstof the master switchbank, through the selector switch E. Furthermore, the superwinding ofthe rela 34 to ground G, as visory relay 70 also energizes and placesthe previously traced. he motor magnet relay springs 72 and 73 incontact, thereby closing 10 again energizes and closes the circuit for acircuit throu h the supervisory lamp 74 the motor magnet. The motormagnet operwhich extends from ground G through the ates as before, andthe wiper 37 [5 carried side switch wiper 75,springs 72 and 73, lamp tothe next contact, and the next tooth of 74 to the battery lead 25,thence through the wheel 48 separates the sprin s 46 and 4?. battery Bto ground (i. The slow-actin re- 15 This operation continues as ong asthe lease relay 6? also carries the spring 76 rom so wiper 37 continuesto find contacts with prothe spring 77 and into contact with the teetingpotential. It will he understood, of spring 78. course. that when themotor magnet 35 thus The foregoing is the condition of the operates, theplunger shaft 36 and all luncentral office switches after the callingsubgers that are in locking engagement wit the scriber removes hisreceiver andbefore the 85 said shaft are moved to a new positionoppodial .is turned. When the dial returns to site an idle-bank terminalsimilar to the one normal position for the first digit 2 the engaged bythe line switch C, and at the firsbselector switch E is operated. Thesame time the bridge-cut-ofi' springs 26 and first digit being 2, theimpulse spring 14 is 29 are separated from the springs 27 and twicecarried out of engagement with the 90 28, respectively, to disconnectthe line conimpulse spring 15. As a result the energizductors from theline switch C. At the in- -ing circuit through the line relay 58 isstantthat the plunger enters the bank the broken twice, and the spring 63comes into following springs are pressed intocontact: contact with thespring 64 twice. After the 80 and 51,, 52 and 53, 5.4 and 55, and 32 andtwo "impulses "are thus delivered the line'flb 33. The enga ement ofthesprings 50 and relay' 58 again energizes and carries the i 51 and 54 an55 extends the-ca ing subs ring 63 into contact with the spring 65.scribers' line conductors 19"and 20 to the previously explained, therelay 67 is a trunk-line conductors56 311(1'57'Whi6h terslow-actingrelay-that IS, slow to deener- 86 minate in the first-selector E. Thisexten-' gize; and; when his energizing circuit is sion of-the -lineprovides an energizing cir: momentaril brokendur ng the yertienlimcnit'for the line'rela 58 of the first-selector. just elivered, the saidrelay'does 'not Thecircuit extends rom ground Gthrongh enor'gize butremains in an operated po the winding 59, side switchwiper 60, trunksition with the springs68 and 76 in contact 40 conductor 57, banksprings 55 and 54, line .with the-springs 69 and 78. Then whenfthe 106conductor-20, transmitter Lprimarywind spring (SS-engages the spring '65two uning 5, impulse springs 14 an 15-, s'pringsl'i'pulses'aretransnpttedto the vertical and. 18, line conductor 19, banksprings 50 net479,-' extend1ng from ground G' throng and 51, trunkconductor'56, side sw tch wiper the springs 63 and to the springs 76 and45 61, through-winding 62'to-the battery lead 78," t rou h the l rivate"magnetrelaygfio, 25, thence through attery B t'of'ground G. through te-wmd g of the'yertlcal magnet Theline relay 58 thereupon energims and-79, contact'po1n t 81 side switch w1per82to operates ,to .earrythesp'rln 63 out of enthe battery lead thence thrbn battery gagement withthe spring and into-en B ground 4G. jflho twoimpu 60 gal ement with thespring 65,'thereby r0 dehvered,'the vertical magnet 19-1sthere'by-115vid ingan energizing circuit for the s ow energized twice, and the shaftw1 rs are acting release relay 67, whichlatter ih t urn "given two' vertcal steps in the we known operates to provide-an energizing circuit forma,nner. It will seen that the private the bridge-cnt-ofi' relay 66oftheline switch-; magnet relay 80 is ncluded inthe ener 56 C. Thiscircuit extends irom ground G eircnltof thevertical'rnagnet 79. V 13120through the prin' 68 and 69, winding of re ay also energ zes, butb'olilg a slow actmg the supcrviso refii y 70 conductor -71, bani; relayit energrzeson the first impulse and springs 53 and 52, bridge-.cut-ofirelay 66, remams'so until all the impulses are'trunstrip or. plungermagnet 24 to the'battery mitbed. ThlS relay, upon ener zing, oper- 60lead 25, thence throu h battery B to ground ates to close the springs 83an 84 1n eon- G. Since the cut-o springs 26 and 27 are tact, whereby anenergizing circuit 18 estabalread in an operated position theenergizalished. through the private magnet 85. This tion 0 the relay 66at this time is without circuit extends from ground G through theparticular function. The trip or longer springs 83 and 84, pr vatemagnet 85.120 the 66 magnet 24, being also included in wt is cirbatterylead 25, thence through battery B m to ground G. The private magnetrelay deener 'izes after the last vertical impulse,

since his energizing circuit is no lon er maintained after the springs63 and (it c isengage. Hence, the said relay again de'e'nergizes,permitting the springs 83 and 84 to disengage, whereby the energizingcircuit through the private magnet 85 is in turn broken. which privatemagnet now deenergizes and permits the side switch to pass f m first tosecond position, permitting the de switch wipers S6 and 82 to engage thecontact points 87 and 88, respectively. The closure of contact betweenthe side switch wiper 82 and the contact point 88 sets up an energizingcircuit for the rotary magnet 89. As shown at L in Fig. 1, a pair otrelays is provided for producing the intermittent energization of therotary magnet 89. The energizing circuit extends from ground Gr throughthe springs 90 and 91, relay 92, winding of the rotary magnet 89,contact point 88, side switch wiper 82 to the battery lead 25, thencethrough battery B to ground G, the rotary magnet and relay 92 energizinin series. The rotary magnet moves the shaft wipers one step, and therelay 92-, upon energizing, places the springs 93 and 91 in contact,whereby a circuit is closed from ground G through the said springs a drelay 95. The relay then operates to separate the springs 90 and 91,therebv breaking'the circuit for the relay 92 and the rotary magnet 89,which restore to normal. When the relay springs 93 and 9-1 disenga thecircuit for the relay 95 is broken an it returns to normal, permittingthe springs 90 and 91 to engage, thereby closing the circuit through therelay 92 and the rotary magnet 89 as before, as long as l the sideswitch wi an 82 remains in second position. From tie foregoing it willbe seen that one relay, upon energizing, ro-. vides a circuit -'0r :1second relay, w ich latter, upon energizing, breaks the circuit for thefirst relay, which then restores to normal, breaking the energizingcircuit for the second relay. the relays L may be allotted to a group offirst-selector switches and used in common to produce the intermittentenergizing of vthe rotary magnets. At M there is shown a like pair of reays for producing the interinittent energization of a group ofsecondselector switches. The said rotary magnet then operates to rotatethe shaft wipers 97, 9S and 99 of the selector E into en agement withthe first contact of the secon level of the selector banks, from whichcontact it is assumed that the trunk-line conductors 100. 101 and 102lead to the second-selector switch F. If the first trunk-line is busy,however. and the wipers have to pass over busy trunk-lines, then as soonas the private wiper 99 engages the first private bank con- -thirdposition. busy trunk-lines the private magnet 85 reand 10.1 which,

It should be stated that I from the spring tact the private magnet 85again energizes, locking the side switch in second position. '1 heenergizing circuit for said private magnet extends from the grouiidedterminal G of the batter B through an occupying switch (not s own),through the private wiper 99, thence through the conductor 103 to theside switch wiper 80, contact point 87, through the winding of theprivate magnet 85 to the battery lead 25, thence through battery B toground G. The private magnet 85, upon thus becoming energized, locks theside switch wiper 82 in engagement with the contact point 88, wherebythe rotary magnet 89 will be energized step by step until the wipers arecarried beyond the last busy trunk-line. At the instant that the privatewiper leaves the last busy contact point the energizing circuit throughthe private magnet 85 is destroyed, and as a result the selector sideswitch passes to If, however, there are no leases the side switch tothird position as soon as the wipers are carried into' engagement withthe first trunk-line. As soon as the side switch passes to thirdposition, as stated, the subscribers line conductors 19 and 20 areextended to the conductors in this case, it is assumed lead to thesecond-selector switch F. The extending of the line occurs, of course,as soon as the side switch wipers 61 and 60 engage the contact points104 and 105, respectively. hen the subscribers line is thus extended tothe selector switch F an energizing circuit is established through theline relay 106 in the same manner in which the energizing circuit wasestablished through the line relay 58 of the selector E when thesubscribers line conductors 19 and 20 were extended through the lineswitch. bank to the trunk conductors 56 and 57. The relay 106, uponenergizing, operates to shift the sprin 107 from the spring 108 to thespring 109; Vhen the springs 107 and 109 engage, an energizing circuitis established through the slow-actin release relay 110. This circuitextends rom ground G through the springs 10? and 109, through the relay110 to the battery lead 25, thence through butt-ery B to ground G.ergizing, operates to shift the spring 111 1'12 to the sp'ring 113, andthe springs 114 and 115 are also closed in contact. his operation of thesecond-selvtor switch F occurs at the instant that the side switchwipers 61 and 60 of the selector switch E pass to third position andextend the subscribers line conductors 19 and 20 to the second-selectorswitch F. When the second-selector switch, therefore, operates, aguarding potential is established at the private wiper 99 for protectingthe se zed trunk-line conductors 100 and 101 against The relay, uponen-' said circuit extending from ground thencethrough battery B toground G.

seizure by another calling first -selector. This guarding potentialextends from ground 6' to the contact point 116, side switch wiper 11?.through the springs 11:: and 114. comlnctor in. to the contact engagedby the private wiper 99. Furthermore. when the first-selector switch l'loperates and the side switch passes to third position, a new energizingcircuit is established through the release relay 6?. This energizingcircuit extends from ground (i at the selector switch i" through thesprings 11.3 and 114. conductor -3. shaft wiper 99. conductor 103.through the side switch wiper 86. contact point 118. relay 6?. thencethrough battery B to ground G. The relay 6? thus remains in an operatedposition with the spring 68 in engagement with the spring 69. but theline relav 58 returns to normal position when the side switch wipers 60and 61 engage the contact-points and 104, respectively. The energizingcircuit through the l ne relay 106 extends from ground G through thewinding 119 to the side switch viper 1'20. thence through the conductor101. conductor 5 and line conductor 26. through the primary circuit ofthe substation. through the line conductor 19. thence through the trunkconductor 56, conductor 100. side switch wiper 121. through the winding12? of the relay 106 to the battery lead 35. thence through hattery B toground 6.. .When the dial returns to normal position totthe second digit'2. this circuit through the, line, relay 106 is interrupted twice whenthe impulse spring 14 is carried out of engagement with the spring 15by'theiimpulse teeth on .the wheel 10. Thelcircuit beinginterrupted'twice. the said relay 106 momentarily 'dee'nergizes. thuspermitting he swing 197 to engage the spring 108, where y an energizingcircuit is completed ..hrough the vertical magnet 122, G" to thesprings10? and 108, springs 111 and 113. through the windingof the privatemagnet rela'v 123, through the winding of the vertical magnet 1122.contact point 124. side switch wiper to the battery lead 25, The

private.=magnet'rela v 123. being included in this circuit. energizesand, since it is a slow-acting relay. remains in an operated positionuntilthe last vertical impulse is delivered. and the relay 1G6 remainsenergized with the spring 107 in contact with the spring 109. wherebythe circuit through the private magnet relay and the vertical magnet 122remains open. When the relay 123 energizes. the springs 126 and 127 arepressed into contact. thcrehy causing an energizing current to Howthrough the private magnet 12%. the circuit extending from ground G"through the springs 10? and 108, through the winding of the privatemagnet 128 to the hattery lead 25, thence through hattery B to ground G.When the relay 123 deenergizes and breaks the energizing circuit throughthe private magnet 128, the private magnet also dei nergizes and permitsthe side switch to pass from first. to second position. \l'hen the sideswitch wiper 125 passes to second position and into engagement with thecontact point 129 an energizing circuit is established through therotary magnet 130 which now operates. as explained in connection withthe rotary magnet 89 of the seicctor switch ii. to select an idletrunk-line leading to the connector switch. After the switch comes torest with the side switch in third position. the shaft wipers 131. 132and 1321 are in engagement with the trunk conductors 134. 121. and 136,respectively. which lead to the connector switch H (Fig. 2). .\t theinstant that the side switch wipers 121 and 12 pass to third positioninto engagement with the contact points 131 and 138. the suhscrihcfisline conductors are extended to the connector switch H. and anenergizing circuit is established through the line relay 139 in the samemanner in which the energizing circuit was estahlished through the linerelay 106 of the selector switch 1" when the side switch wipers of thefirst-selector passed to third position. The energizing circuit throughthe line relay 139 extends from ground G through the winding 14". trunkconductors 13 i. 161 and 57 to the line conductor 20, thence through thesubstation to the line conductor 19. trunk conductors 56, 100 and 134.thence through the winding 141 to the battery lead 25. and throughbattery B to ground G. The line relay' 139, upon energizing. operates tosl 'ft the spring 142 from the spring 143 tothe spring 144, whereby anenergizing circuit is established through the release relay 145extending from groan G through the springs 142 and 144, springs 146 and147, rela 145 to the battery lead 25. thence throng battery 13 to ground'hen the relay 145 energizes, the spring 148 is shifted out of contactwith the spring 149 and into contact with the spring 150, and the spring152' is shifted into engagemerit with the spring 151. This primaryo'ieration of the connector relays 139 and 1 5 occurs at the instantthat the side switch wipers 120 and 121 of the selector F pass to thirdosition and" extend the subscribers line con. uc rs to the connector H.e enga "ment of the springs 151 an tablis es a guarding potential forprotecting the trunk-line conductors 1:34, and 136 against seizure byanother line and second-selector. This potontial'extends from ground Gthrough the winding 153 of the busy-signaling device to the side switchwiper 154 (in second position), springs 152 and 151, conductor 136 tothe private bank contact engaged by the shaft wiper 133. Furthermore,when the side switch of the second-selector F passes to third position anew energizing circuit is established through the release relay 110,said circuit extendin from ground Gr at the connector. switch (F in. '2)through the springs 152 and 151, conductor 136, side switch wiper 15:),conductor 156, from which one branch passes through the relay 110 tobattery, while another branch extends through the contact point 157,side switch wiper 117, springs 115 and 114, conductor 102 to the bankcontact engaged by the private wiper 99 of the selector switch E, thenceto and through the relay 6?, as previously traced. The 0 eration of thedial for the last two cigits afl'ects the connector switch, and when thedial is operated for the third di it 2 the impulse spring 14 is twicecarried out of engagement with the sprin 15, thereby momentarily deenerizing t e line relay 139 twice, whereby t e spring 142 twice enga es thespring 143, thus sending two impu ses to the vertical magnet 158 fromground (i through the springs 142 and 143, springs 148 and 150, privatemagnet relay 159, through the vertical magnet 158, contact point 161,side switch wiper 162 to the battery lead 25, thence through battery Bto ground G The private magnet relay 159 energizes when the firstimpulse is delivered, and since the said relay is slowacting it remainsin an operated position until all the vertical impulses'are sent. Thevertical magnet, upon being energized. operates one step at a time tocarry the shaft wipers 163, 16-1 and 165 two steps to a point oppositethe second level. The relay 159.

lupon ener izing, shifts'the springs 166 and 167 out o engagement, andthe spring 169 is shifted into engagement with t 1e spring 168. \Vhenthe springs 168 and 169 engage, an energizing circuit is establishedthrou h the private magnet 170 from ground 1 through the springs 168 and169. private magnet 170 to the battery lead 25. thence through batterv Bto ground G. The relay 159,being a s ow-acting relay. remains in anoperated position while the vertical impulses are being sent: but afterall the impulses are delivered. and the line relay 139 returns to itsoperated position. the circuit through the relay 159 becomes broken.thus permitting the springs 16? and 169 to return to. normal position.'hen the springs 169 and 168 disengage. the circuit through the privatemagnet 1T0 becomes broken. whereby the said magnet dei nergizcs.permitting the side switch to pass from first to second position. Thecalling Sllll.('1'lllll' now operates the calling device for the lastdigit thereby transmitting ten impulscs and operating the line rc'lay139 ten times. Each tin'ie that the line relay springs 142 and 143cugage, an energizing circuit is established through the rotary magnet161 from ground G through the said springs 1-12 and 143 and the springs148 and 150, through the private magnet relay 159, through the rotarymagnet 171 to the contact point 172, thence through the side switch\viJer 162 to the battery lead 25, and througi battery B to ground G.Again the private magnet relay energizes, as in the previous case,remaining so until all the impulses are transmittal. thereby retainingthe private magnet encrgized also. The rotarv magnet 1T1 thcn operatesto rotate the shaft wipers into cngagement with the desired line #2226.if this line is busy at the time, the connector will be given thebusy-release in the ma nucr to be described, and the calling subscriberis given the busy-signal. thus making it impossible to extend thecalling line into connection with the called line.

Before describing the results that follow when the connector finds abusy line. the description of how a connection is established will becompleted. As soonas the line relay 139 ceases to operate for thc lastdigit theprivate magnet relay 159 deenergizes. as heretofore.explained.permitting. in this instance. the side switch to trip to third position.The result is that the side switch wipers respectively engage theircontact points of the third position. When the side switch wiper 173engages the contact point 174 a guarding potential is completed at theprivate wiper for protecting the seized line from outside interferencewhile the connection is established. This guarding potential extendsfrom ground G to the contact point lT-l. thcncc by way of the sideswitch wiper 173 to the private wiper 165. Not only does this guardingpotential prevent other connectors from calling-in on the same line overmultiples of the normal conductors 175, 176 and 177. but it alsoprovides means for cuergizingthe cut-off relay 176 of the line switchwhereby the said switch C is prevented from :operating when the calledsubscriber removes hisrecciver 179 from the switch-hook 180. It willalso he seen that when the Side switch passed to third position thetrunk-release -conductor 1116 that runs'betwccn thc swoml-sclcctor and gance winding 153 and the side switch wiper 154. The reason for. this isthat the guarding potential from ground G is inter- ,rupted while theline relay 139 is operating,

and there is a possibility of some other selector similar to theselector F stopping on the same trunk-line. After the side switch passesto third. position, however,

there is no such danger, and the potential is provided from ground Gthrough the line relay springs, as stated. Of course, when the sideswitch wipers 182 and 183 engage their third-position contact points 181and185 the calling subscribers line is placed in connection with thecalled subscriber's line over the heavy conductors shown, passingthrough the ringer relay springs 186 and 187 on one side, and 188 and189 on the other side. As soon as connection is thus established theringer relay 190 is energizedover the circuit established 7 when theside switch wiper 162 engages the contact point 191, the energizingcurrent flowing from ground G at the ringer interrupter, through thewindin 192 of the relay 196, through the back-bridge relay springs 193and 191, ringer relay 190, mnductor 195," contact point 191, side switchwiper 162 to the battery lead 25,.thence through battery B to ground (1.The relay 196 thereupon energizes, while the ringer relay 190, which isof lower resistance, remains in normalv position. -The relay 196,

'upon energizing, closes the springs 197 and '"maintains the springs 201and 202 in contact. It will be seen that as the ratchet wheel 200revolves, the energizing circuit of the ringer relay 190 will be brokenperiodically so as not to ring the called subscriber continuously.Furthermore, it will be seen that. each time that the ringci'u relay isenerg zed the springs 186 and 18.? are separi'lri-d from the ringerrelay springs 187 and 15:, thereby breaking the calling line from thecalled line, and pressed into engagcmcnt with the springs 204 and 205which are the terminals of the ringer gen-= orator I.- As a resultringing current is sent over the called line for energizing the bell 206while the springs 207 and 208 are in contact. However, as soon as thecalled subscriber answers, the baclcbridge relay 209 is energized byaflow of current from rvnrnifir] (117 nnnl-unlnninf 17A. eirln exvlfnl'irelay to energize as 1011 relay 209, ringer relay springs 189 and 188,side switch wiper 183, contact point- 185, line wiper164, normalconductor 176, conductor 211-, transmitter 212, primary winding'213,impulse springs 21 4, switchhook sprin'gs 215 and 216, line conductor217, normal conductor 175, line wiper 1118, contact point 181, sideswitch wiper 182, ringer relay springs.186,and 187, winding 218 of theback-bridge iela 209.thence to the batterylead 25 and .tirtlmgh batteryB to ground G. When-once the back-bridge relay 209 is energized theenergizing circuit for the ringer relay 190 is interrupted at a pointbetween the springs 193 and 194, thus making it imposslble for theringer as the called subscriber is on the line. the relay 209 energizes,the springs 146 and 147 also disengage, thereby interrupting .thecircuit which provided a guarding potential to the conductor 136. lVhenthe springs 146 and 147 thus disengage, the relay 221, being included inseries instead of in multiple as before, energizes, but at this timeproduces no effect. The subscribers being thus connected may communicateover the main talking conductors indicated by the heavy lines in Figs. 1and 2 and including on'one side the condenser 219 at the connector H andon the other side the condenser 220. After the, subscribers are throughtalking, if the calling subscriber hangs up his receiver he opens theline circuit -at a point between the springs 17 and'18, therebyinitiating the release of all the switches. This release is broughtabout as follows: At the instant that the circuit is broken between thesaid springs 17 and 18 the double-wound line relay 139 and the releaserelay 145 of the connector H de-nergize. At the instant that theslow-acting relay 14 5 and the line relay 139 deenergize, theenergizing'circuit for the release magnet 222 is closedat a pointbetween the springs 148- and 149 and at another point between thesprings 142 and 113; 1 flow ofcurrent is, therefore, set up from groundG through the springs 142 and. 143, through the springs 148 and 149 tothe off-normal spring 223, to the contact point 224, to the release maet 222. thence through said magnet to the attery lead 25, and throughbattery B to ground G. The release magnet instantly releases theconnector switch shaft; and side switch, thereby breaking the energizingcircuit through the back-bridge relay 209 (if the called subscriber hasnot in the meantime restored his receiver), and also the energizingcircuit through the bridgecut-otl' relay 178 of the called line switchurthermore, when' rating the oil-normal spring 22:52 by sepa- 2-33 fromthe contact point 2%. at which instant the re lease magnet of theconnector is also restored. The operation of the line relay 1 39 and ofthe slow-acting relay 145 not only causes the release of the connector.as la-- scribed. but also the release of the precedin; switches. becausethe ground connection from ground G to the tl'tllllbiclifilSc. conductor136 is interrupted by both of these. relays. Since the release relays(37 and are dependent upon this ground for their energized condition, asalready eX- plained. it follows that they will fall back with thefollowing results: As soon as the release relay 11) of the seoondselector F de't nergizcs. the spring 111 falls back into normalengagement h the spring .112, thereby closing an cmrgizing circuit forthe release mania t 22. from ground (i through the springs HJT and 108,through the springs 111 and 112 to the release magnet .225. thence tothe contact point 226. oll normal spring 2;? to the battery lead thencethrough battery I) to ground G. As soon as the release magnet L33energizes. the secondselector side switch and switch shat't arerestored. which shaft, upon reaching its lowest position. opens arelease circuit at a point between the oil-normal spring .227 and thecontact point 226. whcreliiz the release magnet 2;? is restored also. llhen the release relay (3? of the selector E deenergizes. the springs T6anl T7 are brought into contact. and as a result the energizing circuitfor the release magnet 228 is closed. The energizing current for thisrelease magnet 228 then flows from ground Gr through the springs 63 andG4 and through the said springs 76 and T circuit for the release magnet.

t to the release magnetZiZS, thence through said magnet to the contactpoint .229. off-nornial spring 230 to the battery lead 25. thencethrough battery B to ground G. The release magnet. upon encrgizing, thenrestore. the first-selector side switch and switch shaft. which shaft.upon reaching its lowest position. opens the en ergizingi circuit forthe release magnet 228 at a point between the off-normal spring :ZSI)and the contact point Q29. I urtherniore. when the release relay 6'?-dei nergizes and separates the springs 6S and (if). the energizingcircuit of the hridge-cut-oll.rela in series with the phinger magnet 2+becomes broken. and as a result the lu-idgc-cut-oll' relay and plungermagnet Ll restore to normal position. onscqucntlv the bank springs 52and 52%. as well as the other bank springs oil the line switch areseparated. thus preventing any further action from the trunk. After theswitches are thus restored the calling subscriber can. of course, thenproceed to make nother call.

Returnin now to thal stane of the call called the line this guardingpotential would "i:

be supplied throuizh the connector switch from a ground terminal similarto the ground terminal G in the connector witch H. as already explained;but it the line switch C is calling. a guariiling potential is 8(established from the trunk-line relay ground as in Fig. 1 and thence tothe private bank contact. In a similar manner the line switch protectsthe calling line it when the hank springs 52 and 53 come into contactfrom SE ground G. from which ground connection is established throughthe said bank springs to the private nornial conductor 231. Then fore.when the subscriber sends in the last impulse the private wiper ltifi iscarried 9( onto the grounded contact. and when the slow--acting relaytilt) of the connector dcenergizes. instead of the side switch trippingto third position. as in the case where the line is not busy. theconnector is given the 9f.

luisya'elease as follows: When the private magnet rela 159 (lci ncrgimsand the springs 1611i and 167 engage. an energizing circuit. iscompleted through the release magnet said circuit extending from thebusy or ll grounded private hank contact. private wiper 165. side switchwiper H3. contact point 232 (bearing in mind that the side switch insecond position). springs 1m;

and 16?. normal spring 22 3. contact point 1( 224. through the releasemagnet to the battery lead 2.). thence through battery B to ground G.The release magnet thereupon energizes and operates to restore the sideswitch and shaft wipers to normal position. 11

hen the side switch restores to first positiou. the calling subscriberis given thc bus vsignal. The path of the liusv-sigl'naliiig currentextends from ground ll through the windintr 153 of the induction coil223 i. 1'

through the side switch wiper 154 which is now in lirst position.conductor ri il. side switch wiper i5 3. ringer rcla) springs 1H8 and15th through the condenser 2;" to the trunk conductor l lo. thencethrough the suli- 1i scribcfs station to the line conductor 19 and trunkconductor 134. through the winding: ill of the line rclzrv to thebattery lcad 2 then e through haticry ll to ground 1;.

when the calling sub criber receives thc 1 lHlFl' S-ltllltll heundcratands that the line is busy and hangs up his receiver. The linecircuit is opened. as already explained. with the result that the lineand slow-actin; 1e

lays 139 and of the connector ll deC-ncr- 1 When the line #2220 iscalling, or it releases theconnector) he energizin 'tery H is providedwith a back-release relay.-.

that is. a release relay which so controls a circuit ofthe releasemagnet that when the called subscriber restores-his receiver-to theswitch-hook (before the calling subscriber circuit for the release ma at222 is c o'secl:

-:This back-release is initiated as follows:

\Vhen-the called subscriber answersflhe relay 209 energizes andseparates .the springs 146 and 147, which removes a shunt from the relay221, thus permitting the latter to energize and lace the springs 235 and236 in contact. ow, when the called subscriber restores liis receirerthe. relay 209 deenergizes and permits thesprings 23T and 238 to ena'ge, thereby closing an energizing (II- cuit or the release magnet222'. This circuit extends from ground G through'the springs 237 and 238springs'235 and .236, normal .s rin 223, contact point- 224, throu h t1e re ease magnet 222 to the batead 25, thence through battery B toground G. .The connector release magnet then enemizes and restores theconnector side switli and shaft wi ers to normal po. sition. Therelease 1. the remain ng switches used in establislnng the connection"is brought about when the callin subscriber desired line. '23 of theline switch to V t a o crating,

restores his receiver to the switc -hook.

I In the foregoing it has beenpointed out how the subscriber at A mayestablish con- 'nection with the substation A. Any other: subscriber ofthe entire system may operate the -central ofiice switching mechanism ina similar manner to extend connection to any Itwill be seen that therelay C- is normally om nected with the battery lead 25 through the v'sp'rings 239 and 240:of the -so-called open main ,r lay 241 whichenergizes in multiple ,1; with the motor. magnet 35. jzThe ibi thusputtin relay 2 3 un the energizing circuit in the er the control of therelay 241 is'to'. prevent any. subscriber from operating hishneswitch.While the" master switch 18 to eliminate any possibility of a lineswitch tripping onto a trunk that is already .in use... It will be seenthat when the relay 241 energizes, the sp'rin 239- s separated from thespr1ng240an carried into enga ment with the spring 242,- through lattera busy-Si al may be trans' mitted to. the subscriber 5 station incase-htshould attempt to make a call while the master switch isrotating. It is obvious that if all of the trunks are made busy themaster switch will not stop until some oneaof the.

trunks becomes idle, so that the subscriber not only gets a busytooperate his line switc while it is passing 'olf relay in series, saidmagnet with an armature-harm a finger a apted toal if he attempts fromone point to another, butalso if he tries to call'while all of thetrunks are busy.

It will be seen that the line switch 0 diagrammatically shown in Fig. 1is more fully represented in Fig. 3. In the said Fig. 3 the plun er arm18 more fully shown, controlling by its left terminal the spring 26 andcarrying on the right end the plunger which operates the bank springs,such as the bank springs 50, 5t, 52, 53, 54, 55, 32 and 33.

From the foregoing it will be seen that I provide an improve. and highlyefficient tw'o-wire systemfor automatically trunking calling lines intoconnection with called lines.

What I claim as my invention is 1. In a telephone system, a line, aplurality of trunks,'a plunger for traversing the trunks and connectingthe line with an idle one thereof, a magnet for drawing the pluner intoposition to close the connection, a line relay bridged on the line andcontrolhng said magnet, a bridge-cut-ofl' relay, and a circuit forenergizing said magnet and cut-oil relay in series.

2. In a telephone system, a line, a plurality of trunks, a plunger fortraversing. the

trunks and connecting the line with an idle one thereof, a magnet fordrawing the plunr into positionto close the connectiom-a ine relaybridged on the line and, controlling said magnet, a bridge-cut-ofi.relay a circuit for energizing said magnet rovided open thesprin of sai'cut-off relay.

3. In a telep' one system,- a line, a pluraltrunks and connecting the.line with an idle one thereof, a magnet for drawing the'plunr intoposition to close the connectiomfa. ine relay bridged on the line andcontroland and cutity of trunks, .a. plungerfor traversing the llt Ill

ling said magnet, abridge-cut-oflz" relay ,=and j a circuit forenergizing 'said magnet and cutofi relay in series, said. circuitincluding a third or non-talking conductor of any one of said trunks. 5.In a telephone system, a line, a plurality of trunks, a plunger fortraversing the trunks and connecting the line with an idle one thereof,a magnet for drawing the plunr into position to. close the connection, aine rela bridged on the line and controlling sai magnet, a bridg-cut-ofi' relay, a circuit for energizing saic magnet and cutoil relayin series, and. a third relay, said circuit including normal] opencontacts of said third relay, said re s rovided with an energizingcircuit close uring convercation;

6. In a telephone system, a line, a plural ity of trunks, a plunger fortraversing the trunks and connecting'the line with an idle one thereof,a magnet for drawing the pluniger into 'sition to close the connection,a his relay ridged on the line and controllin said magnet, and abridge-cut-ofi' relay, sair magnet provided with anarmature having afingr adapted to open the springs of col relay. y

7. In a telephone system, a line, a plurality of trunks, a plunger fortraversing the.

trunks and connecting the line with an idle one thereof, a magnet fordrawing the plun- 1 into position to closethe connection, a dim relaybridged on the line and controlling said magnet, a bridge-cutoff relay,a circuit for energizing said magnet and cut-ofi' relay in series, saidmagnet rovidcd with an annature having a finger a opted to 0 en thesprings of said cut-off relay, an a third relay, and said circuitincluding a third or non-talking conductor of any one of said trunks,depending on which one is in use, and inclu ing normall open contacts ofsaid third relay, said dy provided with an energizing circuit closeduring conversation. I

8. In a tale hone-system, a. plurahg of automatic swi ches, trunks to besciz by said switches, and a master switch common to" said automaticswitches said master switch provided with a notched wheel and a motormagnet and ratchet for operating the same, contacts operated by thenotches on said wheel, a circuit for said magnet normally open at saidcontacts, an mterru ter fOfSttid circuit operated b .the said nuignet,and-a relay rovided uu normally 'open contacts conneo ed in parallelwith said first-mentioned contacts.

9. In a telephone system, a plurallt sf 3' said switches, and a masterswitch common to said automatic switches, said master switch providedwith a notched wheel and a motor magnet and ratchet for operating thesame, contacts operated by the notches on said wheel, a circuit for saidmagnet normallyopen at said contacts, an interrupter for saidcireuitecgierated by the said magnet, a relay provid with normall opencontacts connected in parallel wi said firstmcntioned contacts, and awiper operated by said magnet and provided with a bank of contacts eachrepresenting a different trunk and controlling circuit through thewindeaidreley. V

10. In a telephone sgstem, a pair of line conductors, athird con nctor,a selector provided with a lamp signal, a supervisory relay controllinsaid amp, and a slow-acting relay contro lin said supervisory relay oversaid third con uctor.

11'. In a telephone system a called line a connector honing twoselecting motions or seizing said line and for setting up a tall:- ingcircuit from the calling to the called line, a busy test circuit for thecalled line separate from the talking circuit, means for a Jplymg a haspotential to the said circuit w ion the caller line is busy, automaticmeans responsive to said bus potential for releasmg the connector if tiecalled line is busy, and means for controlling said connector over twosides of the talking circuit in series by means of a varying number ofimpulses ilependent upon the digit of the called numver.

12. In a telephone system, calling. and called lines, a connector rescousin to the calling subscriber to seize tie called line, and forsetting up a talking circuit from the calling to the called line, a busytest circuit for the called line, means for up )lymg a bus potential tosaid circuit w ion the called inc is busy; automatic means opcrative torelease the connector if the called subscriber hangs u) his telephoneahead of: the calling subsori r, and means for controlling the connectorover two sides of the talki circuit in series.

13. n a telephone system, subscribers sta. tions including callingmechanism, a plurality of trunk lines, two switches, one switch forselecting an idle trunk line indepeuden tl of any operation of saidcalling mechanism. and thus extend a connection over said solected trimkto the second switch. a mac'- net for maintainin It said first switch incontact with said trun t, means including a circuit extending from saidsecond switch for controlling saul magnet, and means for controllingsaid switches over two sides of a line circuit in series.

14. In a. telephone system, a line. a plurality of trunks, an automaticswitch, a pluner for traversing the trunks and connecting t to line withan idle one thereof to extend connection to said automatic switch, amap;- net for drawing the plunger into position to close connection. andmeans including a circuit extending from said switch for controlling aidmagnet.

12;. In a telephone system. a line, a plurality of trunks, an automaticswitch. a plungerfor traversing the trunks and connecting the line withan idle one thereof to extend connection to said automatic switch. amug!- net for drawing the plunger into position to close connection,means including a circuit extending from said switch for controlliuusaid magnet. and menus for controlling said switch over two sides of theline in series.

16. In a telephone system, a plurality of ating said motor magnet,

, "lines, an automatic switch to a extend a connection over sa dsaidzautomatic F.

.said motor magnet,-an comp'nsmg'a air of springs automatic switches,trunks to be seized h said switches, said automatic switches, a pairoihormally opencontarts, a short-circuit adaptcd to be closed aroundsaid contacts, means [or initially closing said short-circuit to operatesaid master switch, and means for continuing the operation of saidmaster switch through the medium of said contacts.

1?. in a telephone system, a plurality of automatic switches, trunks tobe seized by said switches, a master switch common to said automaticswitches, a pair of normally open contacts, a shorl-dircuit adapted tobe closed around said contacts, means for initially closing saidshort-circuit to operate said master-switch, means for continuing theoperation of said master switch through the medium of said contacts, andmeans for controlling said switches over two sides of a line circuit inseries.

18. In a telephone system, a plurality of automatic switches, trunks tobe seized .by said switches, a master switch common to saidautomaticswitches, a motor magnet for operating said master switch, meanscomprising a pair of springs for initially 03erand indepen ent meanscomprising a pair of circuiting 'said first pair for continuing saidoperation after the initial operation.

19. Ina. telephone sys a pluriailg of automatic switches, trun smt bese' by said switches, a-master switch common to switches, am'otor magnetfor operating sald master switch, ,a pa'1r of springs 'and a relay for"initially operating d independent-means for short circuitmg -said rst "rfor-continuing said operation after the initial operation.

an. Ina.' telephone system, a p

bpmatically means signal Tfor seizing said switch, a supervisory forsaid switch, means signal when said switch is serz for cont lling saidswitch over I of a line circuit in series.

21. In a telephone-system, a plurality of lines divided. into groups, anautomatic switch to automatically extend a'connection over said lines,means for seizing said a h,

' a supervisory signal for said switch, m'eans {-for displaying saidsignal when said. switch is seized, and means for controlling saidswitch over twosides of a line circuit in series. said switch havingmotion in one plane to select groups and motion in an intersectingplaneto find a line in a selected .group.

22. In a telephone system. a line. a plurality of trunks, a plunger fortraversing the trunks and connecting the line with an idle one thereof amagnet for drawing the planger into position to close the connection. a

line relay bridged on the line and control a master switch common tosprings for short idle one thereof, ajnagnet for drawing lurahty of.

'trun and connecting for zg 3am .one' thereof, a mag et and-means twosides ling said magnet, a hridge-cut-ofl' relay, a circuit forenergizing said magnet and cutoll' relay in series, and means forcontrolling said line relay m'rr two sides of the line in series.

23. In a telephone system, a line, a plurality of trunks, a plungerfor'travcrsing the trunks and connecting the line with an idle onethereof. a magnet for drawing the plunger into position to close theconnection, a line relay bridged on the line and controlling saidmagnet. a hridge-cut-oll' relay, a circuit for energizing said magnetand cutof! relay in series. said magnet provided with an armature ha\ing a finger adapted to open the springs of said cut-oil relay, andmeans for controlling said line relay over two sides otthe line inseries.

24. In a telephone system, a line, a plural ity of trunks. a plunger fortraversing the .trunks and connecting the line with an idle one thereof,a magnet for drawing. the plunger into position to close the connection,a line relay bridged on the line and controlling said magnet, abridge-cut-ofl' relay, a circuit for energizing said magnet and cut-oilrelay in series, said circuit including a trunk condoctor, and meansforcontrolling said line relay over two sides'of the line in series.

25. In a telephone system, a line, a phirality of trunks, a plunger fortraversing the trunks and connecting the line with in t a [0D to closethe-conneczidged on the-line. and cut-0E relay, acircnit for energizingsai r'nagn'etand cut-0E relay in rice, sai circuit including a third ornon-trlkingconductor of any one of said trunks, and means forcontrolling saidline relay over two s des of the line in plungerj intoposit 26. In a-telephone system, ralit of trunks, a-plungerfortraversing the the. line with an idle for'drawing the pluner intopos'tion to close the connection, a rela bridged on the line and controlsai 'magnet, a bridge-carrot! relay, a circuit for'energizing sai magnetand cut-- oil relay inseries, a third relay, said circuit includinnormally open contacts of' said third -re ay, said lay provided with anenergiaing circu't closed during conversation, and means, forcontrolling said line relay over two sides of the linein series.

27. In a telephone a line, a plurality of trunks, -a plunger fortraversing the trunks and conhecting the line with an idle one thereof,a magnet for drawing the plunger into position to close the connection,a line relay bridged on the line and controlling said to et, abridge-cnt-ofi relay, said magnet provided with an armature having Ifinger adapted to open the springB of said a line; a plus cutofi' relay,and means for controlling said line relay over two sides of the line inseries. 28. In a telephone system, a line, a plurality of trunks, aplunger .for traversing '5 the trunks and connecting the line with anidle one thereof, a magnet for drawing the plunger into ,position toclose the connection, a line relay bridged on the line and-controllingsaid magnet, a brid e-cut-ofl' relay, :1 circuit for energizing saimagnet and cutoi! relay in series, said magnet rovided with an armatureh aving'a fin er apted to open the springs of said cut-o relay, a thirdrelay, said circuit including a third or nontalkin conductor of any oneof said trunks, depending on which one isin use, and including normallyopen contacts of said third relay, said relay provided with anenergizing circuit closed during conversation, and :0 means forcontrolling said line relay over two sides of the line in series.

29. In atelephone system, a pluralit of 'automatic switches, trunks tobe'seize by.

said switches. and a master switch common into, said automatic 7switches, said master "switch provided with a notched wheel and a }motormagnet and ratchet for operating the same, contacts operated by thenotches on said wheel, a circuit for said magnet norso finally open atsaid contacts, an interrupter for said circuit operated by the saidmagnet, ii relay provided with normally'open' contactsvconnected inparallel with said first- Imentioned contacts, and means for controllingsaid automatic 'switches over two sides of a llnecircuit in ser es.

1 '30. In a. telephone system, a plurality lof :antomatic switches,-trunks to be seize said-switches, and a master switch common.

said automatic switches, said master a motor magnet and ratchet foroperating the same, contacts operated the notches onisaid wheel,alcijrcuit for sai magnetjnor- '45 --mally open at said contacts, aninterrupter provided with a notched wheel and ."ifor said circuitoperated by the said magnet,

- 'farelay provided with normall open contacts connected in parallel witsaid firstmentioned contacts, a wiper operatedby'said 50...inagn'et andprovided with a bank .0 contacts each representing a difl'erenttrunk andcontrolling cirr-uitthrough the winding of said relay, and means forcontrollingsaid automatic switches over-two of a lme at circuit inseries.

531. -In a telephone system, a' line circuit,

repair of line conductors, a third conductor,

' f'a'selector provided'with a lamp silgnlzl, a anmp, a

.jwrvisory relay controlling sai no slow-acting relay controlling saidsupervisory relay over said third conductor, and

means for controlling said selector over two sides of said line circuitin series, j

4,3,2. In a called subscriber hangs up his telephone .magnet, and'meansfor energizing said re- "of said release magnet and a apted to re- 3'36. In a telephone-system, a called line means for controllin telephqnen, i

called lines divided into groups, a connector 06 responsive to thecalling subscriber to seize the called line to establish'a talkingcircuit between two subscribers, automatic means operative to releasethe connector if the 10 ahead of the calling subscriber, and means forcontrolling the connector over two sides of the talking circuit inseries, said connector having motion in one plane to select groups andmotion in a planeat right-angles thereto to fihd a line in a selectedgroups 33. In a telephone system, subscribers lines, a connector switch,means controlled from any one of said'lines for seizing said connectorswitch and for operating said switch to extend a talking circuit to anyother one of said lines, a line'relay for said connector switchenergized over the two sides of the talking circuit in series to controlthe operation of said switch, a release magnet for said connector, andmeans for energizing said ma et when connection is made with a busy ineto release said confor establishing a talklng'circuit with the calledline, a connector for seizing said line, means for controlling saidconnector over two sides of.the talklngcircuit in series, a releasemagnet for said connector, an energizing circuit for saidmagnet, a sideswitch or saidconnector, a relay for controlling the operation of saidside switch and likewise controlling the circuit of said release 10.lease magnet when connection is made witha ,busy line in order torelease said connector.

35. In a telephone system, a. called line,-'a connector for seizing saidline, a release magnet for said connector, a rotarymagnet forcontrollingthe-operation of and switch, a slow acting relay controllinthe circuit main energized while said rotarymagnet is operating, andmeans for energizing said 11a release magnet whenfconnection is made 1with a busy line in order to release said connector.

for establishing a talking. circuit with the ;Illi called line, aconnector. for seizing said line,

said connector over two sides of the tal ing circuit in series, it

-.a release magnet, a side switch having a plurality of positions, arelay for controlling 12 said side switch, a private wiper, and means ifor closingacircuit for said release magnet through said. private wiperand said. side switch while msecond position, whereby said connector maybe releasedawhencon- 126 nection is made within; busy'linel 37.;In atelephone system, a called line, e a" release magnet for said connector.a side switch, a

"slow acting relay controlling the operation at when in second position,to thereby release I said connector when connection is made with a busyline. v i

38. In a telephone system, a called line, a connector for seizing saidline, a release ma et for said connector, a relay for controfi i ng a.circuit for said magnet, and means whereby said relay is normallyshort-circuited.

39. Ina telephone system, a called line, a connector for se1z1ng saldline, a release ma et for said connector, a: relay for com trofii ng acircuit for said magnet, means whereby said relay is normallyshort-circuited, and means for removing said shortcircuit when thecalledsubscriber answers.

' 40. In a telephone system, a called line, a connector for seizing saidline, a release magnet for said connector, an energizing circuit forsaid release magnet, said circuit including normally open and normally,

closed contacts, means for closing said nori -mally.open contacts andopening said norm'ally closed contacts when the called sub-SCI'lbEPflIlSWOIS, and means for again closing i said normally closedcontacts when the called subscriber replaces his receiver upon the hookto thereby release said connector.

41. In a telephone system, a called line. a connector for seizing saidline, a release magnet for said connector, anenergizing circuit for saidmagnet, said circuit including normally open and normally closedcontacts,'a slowacting relay controlling said normall open contacts, asecond relay for controlling said normally closed contacts.

means for energizing said second relay upon the response of thecalledsubscriber to thereby open said normally closed contacts, and toenergize said slow acting relay to thereby close said normally opencontacts, and means for deenergizing said second relay when saidsubscriber replaces his receiver upon the hook to thereby again closesaid normally closed contacts, whereby the c1rcuit for the releasemagnet is closed and the connector released. a

42. In a telephone system, a plurality of subscribers lines, means forestablishing a connection between two of said lines, means for supplyingringing current to the called line, said means including a ringingrelay,

an energizing circuit for said ringing relay including a second relay,means for closing said circuit to energize said second relay but notsaid ringing relay, andmeans for thereafter increasing the How ofcurrent in said circuit to thereby energize said ringing relay to applyringing current to the called line.

43. In a telephone system, a plurality of subscribers lines, means forestablishing a connection between two of said lines, a ringer relay, acircuit for said relay including a second relay having suliicientresist: ance to prevent energization of said ringer relay, ineans forintermittently operating said second relay to thereb increase the flowof current through sail ringer relay,

and meanscontrolled bysaid ringer relay for supplying ringing currentto-the called 44. Ina telephone system, a calling line, a called line, aprogressively movable trunking connector switch for connecting the twoover a talking circuit, a busy test circuit for the called line separatefrom the talking circuit, means for operating said connector over twosides of the talkingcircuitin series to, find the called line, means forsupplying a busy test potential to said test circuit whenever the'calledline-is-busy, and means responsive to said potential for releasing saidconnector.

45;In a telephone system, a calling line, a called line, a progressivelymovable trunking connector switch for connecting the two over, a talkingcircuit, a busy test circuit for the called line, means -for operatingsaid connector over two sides of the talking circuit in series to findthe called line, means for applying a busy test potential to said testcircuit whenever the called line is busy, means responsive to saidpotential for releasing said connector, and a busy signaling circuit forindicating to the calling line that the called line is busy.

46. In a telephone system, a calling line,

a called line, a progressively movable trunking connector switch forconnecting the two over a talkingcircuit, a busy test circuit for thecalled line, means for operating said connectorover two sides of thetalking circuit in series to find the called line, means for applying abusy test potential to said test circuit whenever the called line isbusy,

means responsive to said potential for recuit, means for voperating saidconnector over two sides of the talking circuit in series to find thecalled line, means for applying a busy test potential to said testclrcuit whenever the called line is busy, means responsive to saidpotential for releasing said connector, said last means comprising arelease magnet, and an energizing circuit for said release magnet, saidcircuit comprising in turn a busy test circuit individual to theconnector switch, said energizing circuit controlled by the release ofthe connector.

48. In a telephone system, a group of second selector switches, eachoperative in accordance with the second di it of the called number,trunks to beselected by said second selectors, a pair of relays commonto said second selectors, operating to intermittently interrupt the flowof current through any selector until an idle trunk is found, each relaycontrolling the circuit of the other, a talking circuit, line relays forsaid selectors connected to said talking circuit, and means forcontrolling said relays over two sides of the talking circuit in series.

49. In a telephone system, a plurality of second selector switches, eachoperative in accordance with the second digit of the called number, aplurality of controlling relays common to all of said second selectorswitches, local circuits controlled by said relays, a'talking circuit,line relays for said selectors connected to said talking circuit, andmeans for controlling said relays over two sides of the talking circuitin series.

50. In a telephone system, a switch having vertical and rotary motions,an operating magnet controlling the rotary motion of said switch, anenergizing circuit for said magnet, a pair of relays controlling saidenergizing circuit, means for energizing one of said relays in order toenergize the second of said relays, and means for opening saidenergizing circuit for said operating magnet by the energizing of saidsecond relay while said first relay is energizedf 51. In a telephonesystem, a vertical and rotary motion switch, a vertical operating manot, a rotary operating magnet, a slow acting relay connected in serieswith said vertical operating magnet, 21 second relay controlled by saidslow acting relay. and

means for closing the energizing circuit for said rotary operatingmagnet by first energizing said relays and then dei nergizing said slowacting relay.

. 52. Ina telephone system, a switch having vertical and rotary motions,an operating magnet controlling the rotary motion of said switch, anenergizing circuit for said magnet, a pair of relays controlling saidenergizing circuit, means for energizing one of said relays in order toenergize the second of said relays, means for opening said energizingcircuit for said operating mag net by the energizing of said secondrelay while said first relay is'en'ergized, and m for controlling theoperation of said switclfi over two sides of the line. 53. ,In atelephone system, a vertical and rotary motion switch, a verticaloperating magnet, a rotary operating magnet, a slow acting relayconnected in series with said vertical operatin magnet, a second relaycontrolled by sai slow acting relay, means for closing the energizingcircuit for said rotary operating magnet by first energizing said relaysand then denergizing said slow acting relay, and meansfor controllingthe operation of said switch over two sides of the line circuit inseries.

54. A telephone exchange system com prising telephone lines, automaticconnectors less in number than said telephone lines, selectors less innumber than the telephone lines, subscribers individual switchescorrespondin in number to the telephone lines, subscri ers devices forclosing .the lines to control said individual switches and selectors andconnectors by a varying number of impulses, line circuits by which thesaid individual switches and selectors and connectors are controlled,each line circuit including the two sides of a calling telephone line inseries, said devices having provisions for determining'the number ofimpulses necessary for each di it of the called number, and means forreleasing saidindividual switches and selectors and connectors by theopening of the calling line.

55. A telephone system comprising telephone lines, a plurality of stepby step connector switches less in number than said telephone lines,locking means dependent upon the use of said connector switches forconnecting purposes to hold the same in an oil-normal position, andautomatic means for restoring said connector switches when thrown intoan oil-normal position while idle.

56. A telephone system comprising trunk lines, a step by step firstselector switch adapted to select idle trunk lines. locking meansdependent upon the use of said selector switch for connecting purposesto hold lines, a subscribers step-by-step in-ividual normal positionwhile idle.

59. A telephone exchange system coniprising telephone lines, automaticconnec- 'tors less in number than said telephone lines. selectors lessin number than the telephone lines. provided with means having verticalstep-by-step motion to select different operative levels, depending onthe number called, and rotary step-by-step motion to connect with a linein the selected level, subscribers individual switches corresponding innumber to the telephone lines, subscribers devices for closing thelinesto control said individual switches and selectors and connector linecircuits by-which the said individual switches and selectors andconnectorsla-re controlled, each line circuit including the two sides ofa calling telephone line in series, and means for releasing saidindividual switches and selec' tors and connectors by-the opening of thecalling line. Y

60. A telephone system comprising telephone lines, a p urality ofconnector switches less in number than said telephone lines. providedwith means having vertical motion to select different operative levelsdepending on the number called, and rotary step-by-step motion toconnect with a line in theselected level, locking means dependent uponthe use of said connector switches for connecting purposes to in. anoff-normal position, and automatic means for restoring said'connectorswitches when thrown into an off-normal positron .while idle. v

61. A telephone system comprising trunk lines. a first-selector switchadapted to select idle trunk lines. provided with means having verticalstep-by-step motion to select differ ent operative levels depending onthe number called. and rotary step-by=step motion to connect with a linein-the selected level..locking means dependent upon the use of saidselector switch for connectingpurposes to .hold the same in anoft-normal position, and

automatic means for restoring .said first selector when thrown intosition while idle. a

'62; A telephone system comprising trunk lines. a second-selector switchadapted to select idle trunk lines provided with means having verticalstcp-by-stcp motion to select different operative levels depending onthe number called. and rotary motion to connect with a ine in theselected lcvcl. locking means dependent upon the use of said sch-c torswitch for connecting purposes to hold hold the same calling line.-

a-n off-normal po the same in an oil-normal position, and automaticmeans for restoring said second-selector when thrown into an ofi-normalposition while idle.

63. A telephone exchange system comprising a calling telephone linc.acalled telephone line. means including a plurality of selectors and acmmector for extending connection from the calling line to the calledline, calling mechanism requiring a separate manual operation thereoffor each digit of the called number. operative to transmit suitablecontrolling current for one digit before the said mechanism is manuallyoperated for the next digit. line circuits for controlling the selectors. and a line circuit for controlling the connector. each linecircuit including saidmechanism and the two sides of the calling. linein series.

(H. A telephone ing telephone lines, less in number than said telephonelines. selectors less in number thanithe teleph 'nc lines, subscribersindividual switches c rresponding in number to the tplephone lines,

exchange system cpmpifisautomatic coiinectiirs 8 control said individualswitches and selectors and connectors, comprising a. calling mechanismrequiring a separate manual opnumber, operative to transmit suitable comtrolling current for one digit before the saii'. mechanism is manuallyoperated for the new digit, line circuits by which the said individ nalswitches and selectors and connectors ar controlled, each line circuitmechanism and the two sides of a calling telephone line in series, andmeans for r leasing said individual switches and seleci tors andconnectors by' the opening of the} eration thereof for each digit of thecalled] 65. A telephone exchan e system oompris ing a calling telephoneline, a called tel];- phone line. calling mechanism requiring a separatemanual operation thereof for each digit of the called number, operativeto 110 transmit suitable controlling current for one digit before thesaid mechanism is manually operated for the next digit. means includinga plu 'alit-y of selectors and a connector for extending connection fromthe call ilig line-to 135 the calledline. provided with means havingvertical motion to select dill'crent operative levels. depending on thenumber called. and rotary motion to connect with a line in the selectedlevel. line circuits selectors. and a lbw-circuit for controllingtlnwonncctor. each line circuit including said mechanism and the twosides of the calling line in series.

66. A telcphonc exchange system compris- 125 ing a selector switch.another selector switch provided with a side switch. a hnc rclay forsaid other switch. and means for energizing inchiding'saii forcontrolling the said line relay after said first switch extendsconnection to said other switch, ada )ted to maintain said line relayenergized as ong as the side switch of said other switch remains infirstor second position.

67. In a telephone system, a connector switch, a side switch, a releasemagnet, and another clectromagnet therefor; an energizing circuit forthe said release magnet controlled by said other electromagnet while theside switch is in second position, the said other electromagnetretaining its armature attracted while the side switch is in secondposition to prevent the release of said connector switc 68. In atelephone system, a connector switch; a side switch, a test wiper, arelease magnet, and another electromagnet therefor; an energizingcircuit for said release magnet controlled by said other electromagnetwhile the side switch is in second position, the said otherelectromagnet retaining its armature attracted while said test wiper ispassin over busy contacts to prevent the release 0 said connectorswitch.

69. In a telephone system, a connector switch; a side switch, a releasemagnet and another electromagnet therefor; an ener izing circuit forsaid release magnet contro led by said other electromagnet while theside switch is in second position, said circuit established bydeenergizing said other electromagnet.

, 70. A tale hone system comprising a connector switc ii. line relaytherefor, av release magnet, means whereby if the line relay isdeiinergizedmomentarily the release magnet is prevented from energizing,and means whereby if the line relay deiinergizes for a greater length oftime the release magnet energizes and releases the said connectorswitch.

71. -A tale hone system comprising a connector switc ,a release magnettherefor a slow acti relay, a line relay, and a shaft or said swit fi,an energizing circuit for said slow acting relay controlled by said linerelay, and an energizing circuit for said re lease magnet controlled bysaid slow acting relay and by said shaft, means whereby if said linerelay denergizes said slow acting relay deiinergizes and sets up anenergizing circuit through said release magnet to re lease said shaft toin turn destroy the ener gizing circuit for the said release magnet.

72. A telephone system comprising a series of switches each providedwith a release. relay, a subscribers telephone and line, 'h first switchof said series being allotted to the line, means whereby when asubscriber removes his receiver the release relay of the first switchenergizes and remains energized until the subscriber hangs up, meanswhereby the first switch me be made to connect with the second switc ofsaid series, and

whereby the release relay of said second switch energizes as soon asconnevti i made with said second switch, which second release relayremains energized until the subscriber hangs up, and means whcrchv saidsecond switch may be inade to HIIHICL t with the third switch of saidseries. and whereby the release relay of said third switch thcnencw'izcs and remains cncrgizcd until the subscriber hangs up hisreceiver.

73. .1 telephone exchange system com prising a selector switch, anotherselector switch having a side switch, said other switch provided withmeans having vertical motion to select different operative levelsdepending upon the number called, and rotary motion to connect with aline in the selected level, a line relay for said other switch. andmeans for energizing said line relay after the first-switch extendsconnection to said other switch adaptcd to maintain said line relayenergized as long as the side switch of said other selector remains infirst or second position.

74. In a telephone system, a connector 5 switch for completingconnection to a desired subscribers line; a test wiper, a release magnetand another electromagnet therefor; an energizing circuit for saidrelease magnet controlled by said other electromagnet. said 1 otherelectromagnet retaining its armature attracted while said test wiper ispassing over busy contacts to prevent the release of said switch.

75. In a telephone system, subscribers 7 lines arranged in groups, aconnector switch for electing a group of saidlines and picking outthedesired line in that group, a release magnet, another electromagnetand an energizin circuit for said release ma ct controlle by said otherelectromagnet w ile said switch is picking out the desired line. saidcircuit established by deiinergizing said other clectromagnet.

76. In an automatic telephone system, an automatic progressively movableswitch, a plurality of lines accessible to said switch, said linesdivided into groups, means for operating said switch to elect a groupand means for thereafter operating the switch to 7 establish connectionwith a line in the elected 4 group: means for releasing said switchafter it has been operated, said means including-a release magnet, acircuit for said release magnet, said switch comprising a magnetauxiliary to said release magnet, said circuit controlled by saidauxiliary magnet to mamtain the circuit of the release magnet open whilethe switch is being operated in the elected group to find any particularline in a the elected group.

77. The combination of an automatic switch and a plurality of lines,said lines divided into groups, said having means whereby it may beoperated automatic switch to elect a group and whereby it may thereafterbe operated to pick out a line in the elected group, said switch havinga release magnet and an auxiliary magnet, a circuit for the releasemagnet, said auxiliary magnet having control overthe circuit of therelease magnet to maintain the same open while the switch is operating.to pick out a line in the elected group.

'78,. In an automatic telephone system, an

automatic progressively movable switch, a

plurality of lines accessible to said switch, said lines divided intogroups, means for operating said switch to elect agroup and means forthereafter operating the switch to establish connection with a line inthe elected group: means for releasing said switch after it has beenoperated, said means including a release magnet, a circuit for to electa group and whereby it v.may there-.

after be operated to pick out a line in the elected group, said switchhaving a release magnet and an auxiliary magnet, a circuit for therelease magnet, saidauxiliary magnet having control over the circuit ofthe a release magnet to maintain the same open while the switch isoperating to pick out a line in the elected group, and means forenergizing said auxiliary magnet during the interval that it is holdingthe release circuit open. r

80. In a telephone system, a lurality of selectors, a connector,.release re ays in each ofsaid selectors, and means in said connector formaintaining all of said relays energized. f i

81. In an automatic telephone exchange trunking system, a callingsubscribers line and a walled saibscrihers line, a plurality of switchesfor establishing connection between solid lines, a slow-acting relay ineach of said switches, one of said switchesadapted to supply the talkingcircuit with talking currenn'the said talking current supplying switchcomprising means for maintaining all the said slow-acting relaysenergized.

82. In an automatic exchange trunking switch, a calling line and acalled line, a

plurality of switches for establishing connection between said lines,releasing apparates ,for each of said switches, a release switchesfor'teunking the calling relay for controlling each releasing apparatus,one of said switches comprising means for supplying the talkin'gcircuitwith talk ing current, said one switch also comprising means formaintaining all of said release relays energized.

83. In an automatic telephone exchange trunking system, a callinsuhscribers line and a called subscribers l ne, means including aplurality, of selector switches and a connector switch for connectingthe two lines, a releasing mechanism for each switch and a releasingrelay for'controllingeach releasing machanism, parallel circuits forsaid release relays, and a, line relay for the connector switch, saidline rela adapted to control the parallel circuits 0t? all of saidrelease relays after the two lines are con-' nected.

84; In an automatic telephone exchange trunking system, a callingsubscribers line and a called subscribers line, means includ-'connection between the two lines in a step by-step, manner, a releasemechanism for each switch,-a slow-acting release relay forcontrollingeach releasing mechanism, the slow-acting releasing relay of the lastswitch brought into the connection being adapted to control the circuitofthe slow-acting release relays of all the preceding switches, thereleasing relay of each switch adapted to become energized from theinstant that this switch is brought into use until it is released.

85. In an automatic telephone exchange trunking system, a callingsubscribers line and a called subscribers line, means including aplurality of selector switches and a connector switch for connecting thetwo lines, a releasing mechanism for each switch and a releasing relayfor controlling each re leasing mechanism, parallel circuits for saidrelease relays, and a line relay for the connector switch, said line'relay adapted to control the parallel circuits of all of said releaserelays after the two lines are connected, the releasing relay of'eachswitch adapted to become. energized from the instant that this switch isbrought into use until it is released.

86. In an automatic telephone exchange trunking system, a calling lineand a called line, a plurality of switches'for connecting the callinglinewith the called line, including a switch individual to the callingline, line bank springs for-the said individual line switch included inthe connectin line circuit, and automatic means where y 1f said springsare separated all of thGSWltChGS are released.

mg a plurality of switches for extending 87. In an automatic telephoneexchange,

